Novel disc refiner and method

ABSTRACT

Novel refining disc plate for use in a disc refiner, the plate being characterized by flow channels between the refining bars which flow channels are of substantially constant cross section, thereby to allow constant velocity of fluid through the channels and markedly reduce turbulence within the disc refiner. The diminished turbulence results in better power efficiency, a reduction in maintenance requirements and an improved defiberized pulp product. Most advantageous plates formed according to the invention include a peripheral flow-retarding ring having a number of flow-dividing ribs and flow paths between the ribs, which flow paths are offset at a small angle from the aforesaid channels.

United States Patent 1 1 Gilbert [111' 3,815,834 June 11, 1974 NOVELDISC REFINER AND METHOD Henry S. Gilbert, Andover, Mass.

[73] Assignee: Bolton-Emerson, lnc., Lawrence,

Mass.

[22] Filed: Feb. 12, 1973 [21] Appl. No.: 331,521

[75] Inventor:

[52] 11.8. CI 241/28, 241/260, 241/296 [51] Int. Cl B271 11/08 [58]Field of Search 241/28, 244, 250, 251, 24 l/259.1, 259.2, 259.3, 260,261.2, 261.3, 296

[56] References Cited UNITED STATES PATENTS 2,035,994 3/1936 Sutherland,.lr 241/259.l X 2,156,321 5/1939 Sutherland, Jr 241/251 X 2,651,9769/1953 Sutherland 241/260 Primary Examiner-Granville Y. Custer, Jr.Attorney, Agent, or FirmPearson & Pearson [5 7] ABSTRACT Novel refiningdisc plate for use in a disc refiner, the plate being characterized byflow channels between the refining bars which flow channels are ofsubstantially constant cross section, thereby to allow constant velocityof fluid through the channels and markedly reduce turbulence within thedisc refiner. The diminished turbulence results in better powerefficiency, a reduction in maintenance requirements and an improveddefiberized pulp product. Most advantageous plates formed according tothe invention include a peripheral flow-retarding ring having a numberof flowdividing ribs and flowpaths between the ribs, which flow pathsare offset at a small angle from the aforesaid channels.

11 Claims, 5 Drawing Figures minimum 1914 3315x334 III" NOVEL DISCRE'FINER AND METHOD BACKGROUND OF THE. INVENTION This invention relatesto a novel disc refiner apparatus such as is used in refining of pulp inpaper making operations.

Disc-type refiners comprise opposed, relatively rotating discs, whichmay be two rotors or may be a stator and a rotor. A paper pulp slurry ispassed between the two discs and is defiberized by the shearing actioncaused by the relative rotation of the discs. A primary problemencountered in such operations is to obtain the most effective use ofpower, that is to have a maximum proportion of power converted utilizedin defiberizing and a minimum proportion of power dissipated innonfiberizing power-consuming phenomena within the refiner. Aparticularly troublesome problem with respect to such undesirable powerconsuming losses is the fact that they usually result in a fast wearrate on the refining discs (2) and a consequent further loss inefficiency and, eventually, a shut-down during which time the refiningdiscs must be refurbished or replaced. Indeed in some operations it hasbeen found desirable to change discs after from one to four daysoperation.

It is manifest, therefore, that it would be desirable to providerefining plates which have efficient defiberizing surfaces, but whichwear more slowly. A number of approaches can be used to improve wear andstill obtain effective defiberizing. For example, one can select ahighly abrasion-resistant metal, or one can adopt a yielding elasticsurface or backing material, as did Sutherland in the devices disclosedin US. Pat. No. 2,156,321 of May 2, 1939. In any event, even moreeffective economical solutions to theproblem would be of value in thepaper making industry.

SUMMARY OF THE INVENTION It is an object of the present invention toprovide refining apparatus capable of achieving effective defiberizingof wood pulp and having exceptional wear characteristics.

Another object of the invention is to provide a refining, i.e.defiberizing, disc which is particularly efficient with respect to powerutilization.

. Still another object of the invention is to provide rotary refiningdisc apparatus which yields a higher quality defiberized pulp.

A further object of the invention is to provide a novel, improved paperpulp refining process which markedly reduces the maintenance ofequipment utilized therein and provides a higher quality defiberizedpulp for papermaking.

Other objects of the invention will be obvious to those skilled in theart on reading this disclosure.

The above objects have been substantially accomplished by constructionof a double disc refiner having two opposed rotating refiner discs, eachthe mirror image of the other, which are constructed to have generallyradially extending refiner bars defining channels between them, as isgenerally known in the art. However, these channels are of substantiallyconstant cross sectional area because, as they extend outwardly towardthe periphery of each disc, they become con stantly wider and shallowerin such relative proportion as to preserve their cross sectional area.

It has been discovered that the use of such channels markedly reducesturbulence, increases power efficiency, extends'plate life from about1,000 to 3,000per cent, and yieldsa longer fiber. The longer'fiber isbelieved to be attributable to the relatively small amount of turbulenceand the consequently greater tendency for longitudinal flow along thechannels between the refining bars. Apparently the fibers tend to rollover the bars in radial alignment. This allows a kind of peeling actionalong the axis of an idealized fiber, rather than a cutting actionacross the width of the fiber.

All these advantages are maximized when the peripheral section of therefining disc, i.e. that between the outer circumference and the outletend of the aforesaid channels, comprises a flow-retarding ringconsisting of a series of alternate grooves and ribs disposed along theedge. These ribs and grooves are offset angularly from the refining barsand channels of the central portion of the disc to retard flow. The ringis not a dam but does present a sufficient resistance to flow toincrease the dwell time of the fluid between the refining segments ofthe discs. The flow paths, or grooves, between these ribs are alsoconstant velocity-inducing because of their size, albeit the velocity ofpulp between the ribs of the ILLUSTRATIVE EXAMPLE OF THE INVENTION Inthis application and accompanying drawings, where is shown and describeda preferred embodiment of the invention and suggested variousalternatives and modifications thereof, but it is to be understood thatthese are not intended to be exhaustive and that other changes andmodifications can be made within the scope of the invention. Thesesuggestions are selected and included for purposes of illustration inorder that others skilled in the art will more'fully understand theinvention and the principles thereof and will be able to modify it andembody it in a variety of forms, each as may be best suited in thecondition of a particular case.

IN THE DRAWINGS FIG. 1 is a plan view of a major portion of one segmentof a refining disc constructed according to the invention.

FIG. 2 is a section of this segment taken along line 22 of FIG. 1.

FIG. 3 is a section of this segment taken along line 3-3 of FIG. 1.

FIG. 4 is a section of this segment taken along line 4:4 of FIG. 1.

FIG. 5 is a section of this segmenttaken along line 5:5 of FIG. 1.

FIGS. 3, 4 and 5 are fragmentary inthat they do not show a sectionthrough the entire depth of the disc segment base. These drawings arenot necessarily shown to scale and should be read with the followingdescription to be understood.

It will be understood by all skilled in the pulp refining art that theinvention is being defined with reference to a disc segment formingone-sixth of a circle, that six such segments are ordinarily mounted ona support plateto form a disc for use in a refining unit. It will alsobe understood that such a disc can be used as a stator, or as rotor, oras is of particular advantage with respect to the instant plate with asecond disc cast to be a mirror image of the one shown, one disc beingthe rotor and the other the stator.

With typical pulp, the direction of rotation of the rotor segment shownin FIG. 1 is clockwise and the clearance between the rotor and stator isabout i 0.010

inch. 2

Referring to FIG. 1, it is seen that a refining disc segment is providedupon its face 11 with three holes 12 to accommodate fasteners used toattach segment 10 to a base plate not shown in the drawings. Alsointegrally cast or molded into face 11 are refining bars 14. Bars 14'define, with face 11, flow channels 16. These flow channels arerelatively narrow and deep nearest the center of the disc, i.e. as at 18and in FIG. 5, but the channels widen and become more shallow as seen at20 and in FIG. 4 at their termination nearer the circumference of thedisc. This modification of the channel diameter is a consequence of theshape of the bars 14. In the example shown, bars 14 do not have to benarrow because the increasing circumferential path along the outwardlyextending radial path of the bars provides sufficient room for expansionof the width of the fiow channels. However, the depth of the bars, i.e.the distance from the top of the bars to the face 11 of the disc, mustbe reduced to achieve the desired constant cross sectional area of theflow channels as they extend radially. This is achieved by slanting theface of the bed upwardly as it extends radially. The bars 14 arepreferablyof uniform width throughout their length, as shown in FIG. 1,but may be of progressively reduced width as they extend radially, asshown in FIG. 5.

When using the term radially herein, the term is used in a broad sense.In fact, it is desirable to have the outwardly extending bars offset bya small angle, say 8 from the radius of the circle formed by the disc.

Thus, fibers flowing in a slurry outwardly along channels l6 tend tohave a uniform velocity, are not subjected to turbulence, which isthought to be an inevitable consequence of a changing velocity profile.The fibers, therefore, apparently tend to align axially with the centerline of the channels. This causes the bars to rotate normal to the fiberaxis and, consequently, there is a relatively small amount of fiberbreakage along the lengths of the fibers.

Along the outer periphery of disc segment 10 is a circularflow-restraining ring 22 comprised of a series of ribs 24 which definegrooves, or flow paths, 26 with face 11. Both ribs 24 and grooves 26 areangularly offset from the radius of the disc by about 15. In theexample, there are about 360 ribs spaced along the periphery of acompleted disc, i.e. a disc comprising six 60 segments.

As seen in FIGS. 2 and 3, the flow paths 26 also become somewhatshallower and wider as they approach the periphery of the disc segment.Between restraining ring 22 and refining central portion 30 is anannular area 28 free of ribs and grooves which forms a transition zonebetween the restraining ring 22 and refiner bars 14.

It is to be understood that the following claims are intended to coverall of the generic and specific features of the invention hereindescribed and all statements of the scope of the invention which mightbe said to fall therebetween.

I claim:

l. A disc refiner plate of the type suitable for use in a plurality ofgenerally radially extending bars upstanding above the face of saiddisc;

said bars defining open channels therebetween and said bars graduallychanging in cross sectional area as they extend toward the circumferenceof each disc to maintain each channel at an approximately constant crosssectional area as that channel extends toward the circumference of thedisc.

2. A- disc plate as defined in claim 1, wherein:

said bars and channels terminate at a spaced distance inside thecircumference of said disc;

a circular flow-restraining ring extends around said circumference; and

an annular space is provided between said ring and the terminus of saidbars, which is free of ribs or grooves.

3. A disc as defined in claim 2, wherein:

said restraining ring is formed of a series of spaced ribs raised fromthe surface of said disc and numbering from about 1.1 to 2.0 the numberof said bars on said disc.

4. A disc as defined in claim 3, wherein:

said spaced ribs gradually change in cross section along their lengthand define flow paths, of constant cross sectional area therebetween.

5. A disc as defined in claim 1, wherein:

said open channels become progressively wider and more shallow as theyextend toward the circumference of the disc.

6. A disc as defined in claim 2, wherein:

said open channels become progressively wider and more shallow as theyextend toward the circumference of the disc.

7. A disc as defined in claim 3, wherein:

v said channels become progressively wider and more shallow as theyextend toward the circumference of the disc.

8. A disc as defined in claim 4, wherein:

said channels become progressively wider and more shallow as they extendtoward the circumference of the disc.

9. In a process for defiberizing wood fibers as they are carried in aliquid slurry comprising the steps of passing the slurry between andproximate the center of two refining discs rotating one with respect tothe other, said discs having radially extending refining bars on theworking faces thereof, the improvement wherein all slurry moving towardthe circumference of said discs between said refining bar is maintainedat a constant flow velocity, maximizing the alignment of said fibers insaid channels with said bars, and causing the relative movement of saidbars and said fibers to be substantially normal to the path or rotationof said bars.

10. A disc refiner plate segment having a central portion formed with aseries of integral, upstanding refining bars, each of uniform width,extending outwardly from proximate the center of the plate toward theperiphery thereof, said bars defining, with the face of said plate, aseries of flow channels, each of uniformly decreasing depth anduniformly increasing width from the center of said plate to the outerterminal ends of said bars;

said bars being of uniformly decreasing height above said face from thecenter of said plate to said termian arcuate, flow-retardation ringsegment fixed to the na] ends and the cross sectional area of said flowoutside of said plate, said ring segment having alchannels beingconstant from one end to the other; ternate ribs and grooves angularlydisposed to the 5 bars and channels of said central portion, each ribwhereby constant stock velocity and reduced turbureducing in width andeach groove increasing in lence is achieved. width from the inner end tothe outer end thereof. 11. A disc refiner plate as specified in claim10, plus:

2. A disc plate as defined in claim 1, wherein: said bars and channelsterminate at a spaced distance inside the circumference of said disc; acircular flow-restraining ring extends around said circumference; and anannular space is provided between said ring and the terminus of saidbars, which is free of ribs or grooves.
 3. A disc as defined in claim 2,wherein: said restraining Ring is formed of a series of spaced ribsraised from the surface of said disc and numbering from about 1.1 to 2.0the number of said bars on said disc.
 4. A disc as defined in claim 3,wherein: said spaced ribs gradually change in cross section along theirlength and define flow paths, of constant cross sectional areatherebetween.
 5. A disc as defined in claim 1, wherein: said openchannels become progressively wider and more shallow as they extendtoward the circumference of the disc.
 6. A disc as defined in claim 2,wherein: said open channels become progressively wider and more shallowas they extend toward the circumference of the disc.
 7. A disc asdefined in claim 3, wherein: said channels become progressively widerand more shallow as they extend toward the circumference of the disc. 8.A disc as defined in claim 4, wherein: said channels becomeprogressively wider and more shallow as they extend toward thecircumference of the disc.
 9. In a process for defiberizing wood fibersas they are carried in a liquid slurry comprising the steps of passingthe slurry between and proximate the center of two refining discsrotating one with respect to the other, said discs having radiallyextending refining bars on the working faces thereof, the improvementwherein all slurry moving toward the circumference of said discs betweensaid refining bar is maintained at a constant flow velocity, maximizingthe alignment of said fibers in said channels with said bars, andcausing the relative movement of said bars and said fibers to besubstantially normal to the path or rotation of said bars.
 10. A discrefiner plate segment having a central portion formed with a series ofintegral, upstanding refining bars, each of uniform width, extendingoutwardly from proximate the center of the plate toward the peripherythereof, said bars defining, with the face of said plate, a series offlow channels, each of uniformly decreasing depth and uniformlyincreasing width from the center of said plate to the outer terminalends of said bars; said bars being of uniformly decreasing height abovesaid face from the center of said plate to said terminal ends and thecross sectional area of said flow channels being constant from one endto the other; whereby constant stock velocity and reduced turbulence isachieved.
 11. A disc refiner plate as specified in claim 10, plus: anarcuate, flow-retardation ring segment fixed to the outside of saidplate, said ring segment having alternate ribs and grooves angularlydisposed to the bars and channels of said central portion, each ribreducing in width and each groove increasing in width from the inner endto the outer end thereof.